Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/wtf/ArrayBuffer.h

Index: Source/wtf/ArrayBuffer.h
diff --git a/Source/wtf/ArrayBuffer.h b/Source/wtf/ArrayBuffer.h
index 40252862a473d892fba9574af6f374ab9d26f1eb..feb3b10aa36f9256b9fde84a6af101f9b5b56aa3 100644
--- a/Source/wtf/ArrayBuffer.h
+++ b/Source/wtf/ArrayBuffer.h
@@ -104,7 +104,7 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::create(const void* source, unsigned byteLen
 {
     ArrayBufferContents contents(byteLength, 1, ArrayBufferContents::ZeroInitialize);
     if (!contents.data())
-        return 0;
+        return nullptr;
     RefPtr<ArrayBuffer> buffer = adoptRef(new ArrayBuffer(contents));
     memcpy(buffer->data(), source, byteLength);
     return buffer.release();
@@ -124,7 +124,7 @@ PassRefPtr<ArrayBuffer> ArrayBuffer::create(unsigned numElements, unsigned eleme
 {
     ArrayBufferContents contents(numElements, elementByteSize, policy);
     if (!contents.data())
-        return 0;
+        return nullptr;
     return adoptRef(new ArrayBuffer(contents));
 }